羧酸根阴离子型功能化离子液体对纤维素的溶解性能

doi:10.11944/j.issn.1000-0518.2018.04.170108

摘要/Abstract

摘要：

通过两步法合成了1,3-二甲基咪唑乙酸盐([C₁mim][CH₃COO])和1,3-二甲基咪唑羟基乙酸盐([C₁mim][HOCH₂COO])两种羧酸根阴离子型功能化离子液体。研究了纤维素在这两种离子液体中的溶解性能。结果表明,阴离子的结构对纤维素的溶解性能有明显影响,在120 ℃下,两种离子液体对纤维素的溶解度分别为19.7%和21.2%。通过傅里叶变换红外光谱(FT-IR)、X射线衍射(XRD)以及热重分析(TG)等技术手段对再生纤维素的结构和热稳定性进行表征,表明两种离子液体均为纤维素的直接溶剂,纤维素在溶解及再生过程中晶体结构由I型转变为无定型结构,且热稳定性有所下降。此外,研究发现溶解温度的提高和溶解时间的延长均会导致再生纤维素聚合度的降低。所获得的研究结果为纤维素溶剂体系的开发具有指导意义。

关键词: 离子液体, 纤维素, 羧酸根, 溶解, 再生

Abstract:

Carboxylate-based task-specific ionic liquids(ILs), viz., 1,3-dimethylimidazolium acetate([C₁mim][CH₃COO]) and 1,3-dimethylimidazolium hydroxylcarboxylate([C₁mim][HOCH₂COO]), have been synthesized, and used as the solvents for cellulose dissolution. The results show that the structure of anions has a significant influence on cellulose dissolution; and at 120 ℃, the solubility of cellulose in [C₁mim][CH₃COO] and [C₁mim][HOCH₂COO] can reach up to 19.7% and 21.2%, respectively. The structure and thermal stability of pristine and regenerated celluloses were characterized by Fourier transform infrared spectroscopy(FT-IR), X-ray diffraction(XRD), and thermogravimetry analysis(TGA) methods. These results demonstrate that the two ionic liquids are the direct solvent for cellulose, and also indicate that the transformation from cellulose I to amorphous cellulose occurrs after the dissolution and regeneration processes in ionic liquids. Moreover, further analysis on the degree of polymerization(DP) of regenerated cellulose shows that the dissolution temperature and time have the negative effect on cellulose DP; and higher dissolution temperature or longer dissolution time affords the lower DP of regenerated cellulose. These results may serve as guidance for developing new cellulose solvent systems in the future.

Key words: ionic liquid, cellulose, carboxylate, dissolution, regeneration

马浩, 廖春燕, 樊梅林, 刘薛恩, 滕俊江, 李凝. 羧酸根阴离子型功能化离子液体对纤维素的溶解性能[J]. 应用化学, 2018, 35(4): 449-456.

Hao MA, Chunyan LIAO, Meilin FAN, Xue'en LIU, Junjiang TENG, Ning LI. Dissolution of Cellulose in Carboxylate-Based Task-Specific Ionic Liquids[J]. Chinese Journal of Applied Chemistry, 2018, 35(4): 449-456.

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